Digital audio workstations (DAWs) have existed ever since the invention of the compact disc commercialized applications for the digitization and processing of audio in the early 1980s. Early systems were based upon the storage of the digitized audio on magnetic tape. The linearity and thus inability of tape-based systems to instantaneously fast forward, rewind or play non-contiguous sections of audio without interruption led to the development of disk-based systems. By storing the digitized audio data on a rotating magnetic or optical disk, the disk's head assembly could rapidly be moved to non-contiguous locations much faster than the audio itself needed to be played back. By appropriate buffering of the data coming from the disk, real-time, non-linear playback of audio was possible. A similar development has occurred in the video world, such that nonlinear editing and post-production systems are now commercially available.
Commercial success of DAWs was limited by long development cycles, high cost, and low-performance technology. The popularization of the personal computer made enormous price/performance improvements in DAWs possible. In commercial or professional audio recording studio, the audio recording and playback process is only one part of the overall function of the studio. This process was previously performed by analog or digital tape-based recorder/players. With the price of a digital disk-based solution dropping, and the availability of low-cost, high performance general-purpose purpose digital signal processors (DSPs), it became feasible to include other studio functions within the DAW itself. Such functions as mixing and signal processing are ideal for performance on DSPs. One can see that an eventual goal is to replicate the complete functioning of an audio recording studio within the confines of a DAW.
By building a DAW around a commercially available personal computer three advantages were obtained. First, the development time no longer included designing a controlling computer and associated hardware and software. Second, a familiar and graphical user interface could be presented from which all DAW functions could be easily and intuitively controlled. And third, the expansion bus of the personal computer provided a standard, low-cost way to add additional hardware functionality to the system.
The difficulties now faced by system designers include questions of how to fit all of the hardware needed to emulate the functioning of an audio recording studio into the personal computer, how to partition and connect the functionality most efficiently and cost-effectively, how to design the software that runs on and controls the system hardware, how to integrate the functioning of the DAW with the functioning of the computer itself, and how to allow for system reconfiguration and expandability. Previous inventions have attempted to address only a subset of the above difficulties.
The New England Digital Synclavier Direct-to-Disk hard disk recorder was one of the first commercial attempts. It succeeded in producing a relatively low performance audio recorder. It was extremely expensive, being made of entirely custom components, and lacked internal mixing, signal processing and expandability. It was, however, well integrated with its internal sampling processor. The Synclavier consisted of a plurality of hard disk modules, each one adding more tracks of hard disk playback and recording. The hard disk modules all connected into a central controller that allowed a very limited pre-scripted level and pan control during playback. There was no signal processing available or possible within the system, nor was there a connection bus. There was a sampler module integrated with the system and, in fact, the level and pan controls of the outputs of the sampler module were used to process the hard disk playback data.
The SoundDroid from Lucas Film (DroidWorks), and its Audio Signal Processor (ASP) was another early attempt. It combined a disk controller and signal processors, but it again was built from custom components, and never achieved commercialization. It did not include a digital sampling module, nor was expansion designed into it. DroidWorks is a division of Lucas Film. In a November 1986 Audio Engineering Society convention preprint entitled "An Optical Disk Recording, Archiving, and Editing Device For Digital Audio Signal Processing" by James A. Moorer and Jeffrey Borish, a device called a DAB, or digital audio board, is described. It is essentially a VME circuit board that has disk and I/O interfaces and a DSP on board. More than one could exist on a back plane of a computer, but each board was essentially autonomous. All audio has to be routed through a single DSP on the board. This board was designed mostly as an I/O board for a larger SoundDroid system. The SoundDroid is discussed in "Digital Audio Processing Station: A New Concept In Audio Post-Production" by James A. Moorer, et al., Journal of The Audio Engineering Society, 34:6, June 1986, pp. 454-463.
The ASP board is another component of the SoundDroid system. The system consisted of multifunction cards but with very little communication between them. Rather than an integrated connection bus, they have general purpose EtherNet interfaces, to use mainly for control as opposed to audio transfer. Audio processing occurs only within individual boards in the system. RAM-based polyphonic sample playback is not performed. It is understood that the product never was completed or produced.
The Pro Tools I System made available by Digidesign, Inc. contains a disk interface card with no I/O, multiple I/O cards that also had two DSPs on them used for dedicated mixing and signal processing, and a sampler card that has no digital outputs. The system was modular, but had no digital audio connection bus nor a general purpose pool of DSPs.
The AudioFrame 1000 from WaveFrame of Boulder, Colo. (now owned by TimeLine Vista Inc. of Vista, Calif.) was a 24 channel hard disk recorder based upon a set of custom circuit boards, but the whole set of boards was controlled by a commercially available IBM-type PC. It had a disk interface, a sample playback processor, and a signal processor, as well as a connection bus to interface at least some of these units. However, the signal processor was dedicated to performing specific functions such as equalization and mixing and the system did not allow customization via adding and removing modules.
Spectral Synthesis Inc. Of Woodinville, Wash. produced a pair of boards that fit inside a commercially available IBM-type PC. The audio frame consisted of a custom bus and card cage attached via an interface card to, as mentioned, an IBM-type PC which is used only for control and user interface. The card cage could accommodate one each of three different card types: a hard disk recorder card, a sampler card and a DSP card. However, there could not have been more than one of each card type and no further DSP card could be mounted on the system. The DSP card performed mixing, EQ, reverberation and compression. It was fairly reconfigurable, but only within that one card. A 64 time slot TDM bus connected the three cards, so that hard disk data and sampler data could be mixed together and processed. The system allowed 12 channels of hard disk playback and recording, and a fixed, limited amount of signal processing. There was a connectivity bus between the two cards, but it was very limited in capacity and not designed for expansion. While the system was not expandable, the connector between the cards implemented some type of multiplex bus of about eight time slots that pass data between the two cards.
U.S. Pat. No. 5,357,511 issued Oct. 18, 1994 to DiNapoli et al. describes not a DAW, but a digital mixing console. The modules of this console were all identical, and each perform all the individual system tasks of 1/0, mixing and routing. As can be ascertained from the patents, the user could only add more of the same functionality. Hard disk recording and sample playback are not a part of this system. The patent, however, does disclose a connection bus for interconnecting the modules in the system.
Another company, Sonic Solutions of Novato, Calif., currently produces a system that includes a disk controller, a DSP processor and I/O processor on a single NuBus card. A number of such identical multifunction NuBus cards may be provided to fit into Apple Macintosh computers. The cards have a type of very low capacity bus connected between them to allow several channels of data to be sent to up to one more cate per channel for processing. The code running on the DSP processors is somewhat configurable, but the DSPs are allocated to specific functions and are not implemented as a plurality of general purpose DSPs, as in the present invention. It is only expandable in a limited way to two more of those cards for processing two channels of audio, and does not incorporate sample playback processing described below in reference to the present invention. There is no specific or equivalent to a connection bus for the cards within the system, and it is believed to use a private disk controller system, so their disks and files cannot be seen by the user of the host computer.